Bulking filamentary strand by false twisting



April 22, 1969 N. E. LLOYD 3,4

BULKING FILAMENTARY STRAND FALSE TWISTING FiledDec. 16. 1964 United States Patent 3,439,485 BULKING FILAMENTARY STRAND BY FALSE TWISTING Neil E. Lloyd, Rock Hill, S.C., assignor to Celanese Corporation of America, New York, N.Y., a corporation of Delaware Filed Dec. 16, 1964, Ser. No. 418,673 Int. Cl. D01h 13/26; D02g 3/02 US. Cl. 57-34 Claims ABSTRACT OF THE DISCLOSURE A novel bulked filamentary strand is provided in a method of bulking a filamentary strand wherein the strand is false-twisted by means of a false-twist friction tube and the twist is heat-set by an improved process of l1eat-setting.

This invention relates to a method of and apparatus for bulking a filamentary strand. More specifically, this invention relates to a method of and apparatus for bulking a filamentary strand by false twisting said strand. By the expression filamentary strand is meant any filamentary structure comprising either continuous filaments, singly or twisted together in the form of yarn, or yarns spun from staple fibers, any of which are intended for textile uses.

It is known to bulk a filamentary strand by false twisting the strand and heat setting the false twisted strand. Thus, for example, in US. Patents Nos. 2,936,567 and 2,936,570 there is described such a method wherein an improved twist tube is used. The disclosure of these two patents generally refers to heat setting the false twisted yarn by means of radiant or infrared heating; however, in Patent No. 2,936,567, there is also disclosed heat setting of the yarn by contacting it with an electrically heated metal plate. In these patents, in no examples are throughputs in excess of 300 feet per minute disclosed and when the electrically heated metal plate is used throughputs of between and 60 feet per minute are disclosed. In Patent No. 2,936,570, though in the examples the yarn speed is only 265 feet per minute it is proposed that speeds of 1000 feet per minute and more may be attained.

In accordance with the present invention, there is provided in a method of bulking a filamentary strand comprising false twisting a filamentary strand by applying thereto torsional forces, heat setting said strand while at least partially holding the false twist in said strand, then relaxing said torsional forces, the improved heat setting which comprises moving the false twisted strand longitudinally in a substantially helical path in contact with a heated surface; and allowing thestrand to roll on said surface, said rolling being caused by transverse frictional forces applied to said strand by said surface. Similarly in accordance with the present invention there is also provided in an apparatus for bulking a filamentary strand comprising means for applying thereto torsional forces and means for heat setting the strand while at least partially holding the false twist in said strand, improved means for heat setting comprising a member having a heated surface which provides a helical path of contact for said strand. In a preferred embodiment of the present invention, the member is a cylinder.

In accordance with a further aspect of the present invention there is provided a method of bulking a filamentary strand comprising providing a toroidal surface having a filamentary strand contacting portion, at least part of said filamentary strand contacting portion having a high coeflicient of friction with respect to said filaice mentary strand; longitudinally moving a filamentary strand toward said toroidal surface in a helical path of contact with a heated surface; rotating said toroidal surface about the axis of generation of said toroidal surface; longitudinally feeding said strand from said heated surface into initial contact with said toroidal surface at an entry angle of from about 30 to longitudinally moving said strand along and in contact with said toroidal surface in the axial direction; and withdrawing said strand from final contact with said toroidal surface at an exit angle of from about 30 to 90. In a preferred embodiment of this method, said path of contact of said strand with said heated surface is arcuate; and said strand is allowed to roll on said arcuate surface, said rolling being caused by transverse frictional forces applied to said strand by said surface which, preferably, is rotated in the direction of yarn travel. Similarly there is also provided in accordance with the present invention apparatus for bulking a filamentary strand comprising a twist holdback means a contact heating member; means for heating said member; a rotatable ring having inner surfaces for operating upon a filamentary strand, at least part of said inner surfaces being comprised of a material having a high coefficient of friction with respect to a filamentary strand; means for moving a filamentary strand longitudinally in contact first with said twist hold-back means, then from said twist hold-back means into contact with said contact heating member, and then from said contact heating member to said inner surfaces. In a preferred embodiment of this apparatus said contact heating member has a cylindrical configuration, which configuration provides said strand with a helical path of contact.

The drawing is a simplified isometric illustration of an apparatus according to the present invention.

In the present specification and claims the term toroidal surface is not being used in a strictly mathematical sense. Thus, the term is being used to denote a surface which is roughly convex and which defines an annulus, e.g., the exposed surface of bushing Ill in US. Patents Nos. 2,936,567 and 2,936,570. The toroidal surface may be said to have an axis of generation in the mathematical sense which in the practical sense will generally correspond to the axis of the annulus. The angle between this axis and a line :defined by a filamentary strand approaching contact with the toroidal surface may be said to be an entry angle; and the angle between the same axis and the line defined by a filamentary strand being withdrawn from contact with said toroidal surface may be said to be an exit angle. The term a material having a high coefiicient of friction with respect to a filamentary strand is herein used in the same sense as the term a non-abrasive material having a high coefficient of friction with the textile filament is used in US. Patents Nos. 2,936,567 and 2,936, 570. In terms of apparatus, the above referred to toroidal surface may best be mechani cally embodied and defined as rotatable ring.

The drawing is a simplified illustration in isometric form of an apparatus according to the present invention. The present invention now will be further described by means of a detailed explanation of the drawing as follows:

From supply package 10, yarn 11 is led over guides 12 and 13 in succession and then over twist hold-back guide 14. From twist hold-back guide 14 yarn 11 traces a helical path in contact with and around half to three quarters of the circumference of hot roll 15. Hot roll 15 is a driven, hollow, hot oil-heatable or electrically heatable roll with a conventional hot oil circulating and temperature regulating system or a conventional electrically heating and temperature regulating system (not illustrated) servicing and operatively connected to it. From hot roll 15 yarn 11 is led through friction twister tube 16. Friction twister tube 16 (which provides the toroidal surface referred to above) is driven and may be of the construction disclosed in U.S. Patents Nos. 2,936,567 and 2,936,570. From friction twister tube 16, yarn 11 is guided to a conventional set of take-up rolls 18 and 19. Rolls 18 and 19 are in nipping relation; roll 18 is driven and in turn drives roll 19. The surface speed at which roll 18 is driven regulates the rate at which the yarn is processed. Yarn 11 passes over guide 17, under and in contact with roller 18, over guide 20 and over and in contact with roll 18 and through the nip formed by rolls 18 and 19. Finally, yarn 11 is taken up as a conventional package 21 on a conventional surface winder apparatus which in simplified form is represented as driven rolls 22 and 23 which rotate the package (e.g., package 21 may be a cone and rolls 22 and 23 may represent a Foster 102 Cone Winder; alternately, package 21 may be a tube package rotating on a take-up spindle such as would be found on a Leesona 959 winder; alternately, package 21 may be a bobbin rotating on a spindle and rolls 22 and 23 may be considered to be a ring traveler winder apparatus). All of the guides except twist hold-back guide 14 are conventional rod-shaped ceramic guides or may be ceramic or plastic wheel or roller guides equipped with ball bearings; twist hold-back guide 14 is a conventional ceramic guide but is of the knife edge type in order that it most effectively serve as a stopping point for the twist. Upstream of the twist hold-back guide a magnetic whorl or disc tension device or magnetic hysteresis tensioner or similar tension device (not shown) may be used, set for a tension of preferably from about 3 to 30 grams. Also, two or more of such tensioning devices may be used in combination so as to minimize variations in tension of the yarn fed to the processing arrangement herein described.

By the practice of the present invention it is possible to impart varying degrees of false twist to multifilament or monofilament textile yarn travelling at high linear processing rates up to 1500 meters per minute or more and to set this false twist in the yarn by applying heat to the yarn while it is in the false twisted state. The processing arrangement described here then allows the yarn to cool while it is in the false twisted state. Immediately following the false twisting step the yarn is pulled from the twist tube and as the yarn emerges from the twist tube the torsional force applied by the twist tube is relieved and the yarn becomes untwisted and is taken up under tension varying from to 40 grams (in nontwisted condition) onto take-up roll 18. As the yarn leaves take-up rolls 18 and 19, tension on the yarn is relaxed, and the yarn is 4 packaged (wound) in this state of relatively reduced tension. Following the false twisting, heat setting, cooling and untwisting operations, each individual filament in the yarn tends to coil and return to the highly twisted state in which it was heat set. This coiling effect of individual filaments causes a separation of the filaments, and the combined coiling and separation effect increases the bulk and subsequently reduces the overall length of a given weight of yarn. Also, to some extent (the degree of which is dependent upon the type of yarn being textured) the combined effect of coiling and bulking of individual filaments produces a yarn that is mechanically contracted (coiled) and thus can be stretched and will, when relaxed, return to its original prestretched length.

The method and apparatus whereby the yarn is heat set is particularly important. In the prior art as exemplified by US. Patents Nos. 2,936,567 and 2,936,570 as pointed out above it was believed that maximum processing speeds would be about 1,000 feet per minute which is of course only about 300 meters per minute. According to the present invention much greater processing speeds are achieved due largely to an improved heat setting method and apparatus of the present invention. In a preferred embodiment of the present invention a hot roll as illustrated in the drawing is used to effect the heat setting. The hot roll is maintained at a temperature of from about 200 to 800 F. and preferably from about 250 to 550 F.; this temperature of course is directly related to the processing speed of the yarn. However, it is not the use of a hot roll per se which brings about the full improvement according to the present invention. The manner in which the twisted yarn is brought into contact with the roll is important. The yarn contacts from about 240 to 270 degrees of the circumference of the roll and preferably from about 243 to 265 degrees.

The yarn tends to travel in a helical path during its contact with the hot roll due to the back twisting effect of the friction twister tube through which the yarn is passed after contacting the hot roll; this back twisting effect tends to make the twisted yarn crawl along the surface of the roll in a direction parallel to the axial centerline of the roll; (similarly, back twisting effect causing the twisted yarn to crawl along the surface of the roll could also be introduced by a conventional match-stick type false twist spindle instead of a friction twister tube). Such a helical path may be conveniently provided for simply by withdrawing the yarn from contact with the hot roll at a point axially removed from the point at which the yarn is introduced into contact with the hot roll. The term axially as used in the present context of course refers to the hot roll. Because of the helical path the frictional force exerted by the surface of the hot roll on the yarn has a component which is parallel to the axis of the hot roll. This force component causes the yarn to roll, generally about ,3 to inch, back and forth across the hot roll surface as the yarn travels in its helical path of contact with the hot roll surface. This rolling action is highly advantageous because it results in better transfer of heat from the roll surface to the entire circumferential surface of the yarn by conductive effect. The rolling action and the fact that preferably the surface of the hot roll is driven in the same direction and at the same linear speed or at linear speeds in excess of the linear speed of yarn being processed on the hot roll allows for much greater yarn processing speeds than would otherwise be possible. It is preferred that the hot roll radius be from about 1.5 to 5.0 inches. It is preferred that the displacement of the yarn along the axis of the hot roll (i.e., transverse displacement) during the yarns contact with the hot roll be from about 1.5 to 5.5 inches.

Processed yarn issuing from the hot process roll is pulled through the friction twister tube and onto the take-up rolls preferably at tensions ranging from about 5 to 40 grams as measured between the take-up roll and the friction twister tube. Tension control in this system is important because if the yarn is not held with sufiicient tension against the working surfaces of the friction twister tube and the hot roll, then there will not be sufficient frictional resistance between the yarn and the friction twister tube to cause twist to be inserted in the yarn, nor will there be sufiicient' frictional resistance between the twisted yarn and the surface of the hot roll to allow the yarn to assume a helical path of travel along and cause it to roll across the surface of the hot roll. The driven take-up roll functions as a positive takeup device and is used to control the rate of yarn process ing. The other take-up roll is functionally a hold-down roll which creates a nip with the other roll and prevents slippage of the yarn on the surface of the other roll. Downstream of the hold-down roll tension on the yarn is relaxed preferably to a value of less than one gram and the yarn is packaged (wound). In this latter state of relaxed tension the yarn bulks and consequently the length per unit weight of yarn is reduced. In winding the yarn an overfeed technique may be used in which the linear speed of the yarn as it is wound onto the package is generally on the order of about 5 to 25% less than the speed at which the yarn is being processed through the friction twister tube and around the heated process roll. This produces a soft package. For yarn materials (such as secondary cellulose acetate or cellulose triacetate) which have a relatively poor memory," this overfeed winding technique, wherein the yarn is wound on a takeup package in a relatively relaxed state with a tension generally on the order of about one gram or less, is preferable. However, for yarns which has a good twist memory (such as the polyamides, e.g., nylon-66, and linear polyesters) it is permissible to package (wind) the textured yarn produced from this system at about the same speed (or even at a greater speed) at which it is processed, at tensions generally on the order of about 3 to grams to produce a hard package.

False twist is imparted to the moving yarn by the rotating twist tube, the speed of rotation of which preferably is from about 5,000 to 50,000 r.p.m. or more depending upon the desired twist level. This false twist extends back around the rotating hot process roll to the knife-edge ceramic hold-back guide which preferably is located immediately upstream of the hot roll. Hence, the yarn is in a twisted state as it goes onto the surface of the hot roll. The yarn has essentially the same number of turns per inch of false twist at its final point of contact with the hot rolls surface as at the twist tube iself. Thus between the twist tube and the point of final yarn contact with the hot roll surface the number of turns per inch of false twist is constant. Upstream of the twist holdback guide there is no false twist in the yarn. Immediately downstream of the twist hold-back guide the number of turns per inch of the false twist is at its minimum and may amount to only 50 to 95 percent of the false twist level (i.e., turns per inch) the yarn has at the point where it leaves the hot roll, depending upon the type of yarn being processed, the speed of processing, and the degree of false twist being thrown into the yarn by the twist tube. Between the twist hold-back guide and the point of final yarn contact with the hot roll surface the number of turns per inch of false twist continuously increases in the direction of yarn travel, reaching a maxi mum value at the point where the twisted yarn leaves the hot roll.

The twisted state of the yarn on the hot roll surface is another factor which contributes to the efficiency of the heat setting operation of the present invention and thus to the greater processing speeds which are thereby obtainable. More importantly, the variable degree of false .twist in the yarn as it goes around the hot roll in contact with it causes the yarn to be heat set at variable levels of false twist and this effect results in the production of a textured bulk yarn, or bulk-stretch yarn, or stretch yarn with very unusual qualities of hand, bulk and texture, in that textured multifilament yarn, in particular, produced by the method and apparatus of the present invention contains individual filaments that are randomly curled, coiled and crimped and relatively difierent from adjacent filaments with regard to the degree of coil, curl, or crimp of such neighboring filaments or fibers. This randomized character of curl, crimp and coiling of individual filaments imparted to the whole yarn end by this method of processing extends to the yarn unique and unusual qualities that make it comparable to natural fibers. It may be noted that because of the rolling action of the yarn on the hot roll surface, which rolling action is described above, the yarn may tend to roll off the hot roll surface. Thus, for example, in the drawing the yarn is taken off the hot roll surface at a point which is to the viewers left of the point at which it is introduced to the hot roll surface and therefore the yarn may tend to roll off the hot roll surface at the left-hand end. Any simple mechanical expedient will remedy this situation. Thus for example, a metal or ceramic rod perpendicular to the axis of the hot roll may, in this instance, be positioned right next to the left-hand end of the hot roll and thus as the yarn approaches the left-hand end it will contact the rod and thereby be pushed back toward the center of the roll surface; this may occur repeatedly.

Yarn fed to the twist hold-back guide 14 may consist of a plurality of threadlines comprised of two or more individual ends of multifilament or monofilament yarn originating from individual supply packages of nontextured yarn. These multiple ends would normally be combined and brought together as one strand at guide 13. Immediately downstream of guide 13 and upsteam of false twist hold-back guide 14, the multiple ends are simply gathered together as one group of parallel strands. Immediately downstream of false twist hold-back guide 14 the multiple strands become wrapped around one another in a false plyed, highly false twisted spiral configuration and appear as a single threadline. The individual ends of multifilament or monofilament yarn making up this false plyed, false twisted, multiple end threadline are thus heat set, or relaxed in this highly false twisted state by contact with the hot roll by the means described above. The plurality of twisted ends forming the false plyed, false twisted single strand extends to friction twister tube 16 in this case. Immediately downstream of friction twister tube 16, the multiple ends of multifilament or monofilament yarn making up the false plyed, false twisted single strand become both unplyed and untwisted and therefore separable, and immediately downstream of friction tube 16 and upstream of the take-up roll 18 the multiple ends are simply gathered together in an untwisted, unplyed state. After passing downstream of the nip formed by contact of the presser roll 19 and the takeup roll 18 the individual ends that made up the compositely processed, multiple end threadline may be separated and drawn off and wound on separate take-up packages in the manner previously described for a single end of multifilament or monofilament yarn subjected to the yarn texturing process herein described. Alternately, the individual ends of processed multifilament or monofilament yarn derived from the combined threadline may he wound as individual ends on the same package, or as a recombined strand wound on the same package.

The invention will now be further described by reference to the following examples. It is to be understood that whenever numerical values are herein assigned to the number of turns per inch of false twist such numerical values represent the state of the yarn at the twist tube.

Example 1 A 200 total denier, 34 filament, 3 turns per inch of Z- twist cellulose triacetate yarn having a radius of 0.0043 inch is processed by an apparatus as shown in the drawing. The hot roll has a four inch radius and a six inch width. The yarn is introduced into contact with the hot roll surface about at the middle of the surface and allowed to roll to the observers left; the yarn is withdrawn from the hot roll surface about 1 /2 inches from the left-hand edge of the hot roll, a vertical metal rod defining this limit; 17% inches of the yarn is wrapped about 242 of the hot roll. The surface temperature of the hot roll is 365 F., and the hot roll surface speed is 234.9 meters per minute. The twist tube has an internal diameter of /3 inch and rotates at 10,100 r.p.m. and the yarn has an entry angle of 43 and an exit angle of 56. Take-up roll 18 has a surface speed of 204.4 meters per minute and the yarn is packaged at 167.8 meters per minute. The theoretical false twist is 93 turns per inch.

Example 2 A total denier, 16 filament, 3 turns per inch Z- twist secondary cellulose acetate yarn having a radius of 0.0027 inch is processed by an apparatus as shown in the drawing. The hot roll has a 4-inch radius and a 6- inch width. The yarn is introduced into contact with the hot roll surface about at the middle of the surface and is allowed to roll to the observers left; the yarn is withdrawn from the hot roll surface about 1% inches from the left-hand edge of the hot roll, a vertical metal rod defining this limit; 17 /3 inches of the yarn is wrapped about 242 of the hot roll. The surface temperature of the hot roll is 315 E, and the hot roll surface speed is 208.9

'meters'per minute. The twist tube has an internal diameter of /8 inch and rotates at 8,100 r.p.m. and the yarn has an entry angle of 43 and an exit angle of 56. Takeup roll 18 has a surface speed of 199.8 meters per minute and the yarn is packaged at 163 meters per minute. The theoretical false twist is 119 turns per inch.

Example 3 l A 55 total denier, filament, 3 turns per inch Z-twist cellulose triacetate yarn having a radius of 0.002 inch is processed by an apparatus as shown in the drawing. The hot roll has 9.4-inch radius and a 6-inch width. The yarn is introduced into contact with the hot roll surface about in the'middle of the surface and is allowed to roll to the observers left; the yarn is withdrawn from the hot roll surface about'Vs' inch from the left-hand edge of the hot roll, a vertical rod defining this limit; 17 /8 inches of the yarn is wrapped about 242 of the hot roll. The surface temperature of the hot roll is 280 F. and the hot roll surface speed is 343 meters per minute. The twist tube has an internal diameter of /s inch and rotates at 8,250 r.p.m. and the yarn has an entry angle of 43 and an exit angle of 56. Take-up roll 18 has a surface speed of 299 meters per minute and the yarn is packaged at 261 meters per minute. The theoretical false twist is 110 turns per inch.

Example ,4

In the same manner is processed a 70 total denier, 17 filament, /2 turn per inch Z-twist semidull nylon-66 yarn (which, it may be noted, has a radius of 0.0032 inch) at a hot roll temperature of 399 F., a hot roll surface speed of 500 meters per minute and a twist tube speed of 13,250 r.p.m.; the theoretical false twist is 65 turns per inch.

Example 5 The Example 4 process is carried out but at a rotor speed of 15,800 r.p.m.; the theoretical false twist is 78 turns per inch.

Example 6 In a similar manner, there is processed a 70 denier, 34 filament, A2 Z-turn per inch semidull nylon-66 yarn (which, it may be noted, has a radius of 0.004 inch) at a hot roll surface temperature of 399 F. and hot roll surface speed of 500 meters per minute and at a twist tube speed of 15,000 r.p.m.; the theoretical false twist is 60 turns per inch.

Example 7 The Example 5 process is carried out but at a twist tube speed of 18,000 r.p.m.; the theoretical false twist is 72 turns per inch.

Example 8 Similarly there is processed a 40 total denier, 13 filament, /2 Z-turn per inch semidull nylon-66 yarn (which, it may be noted, has a radius of 0.0025 inch) at a hot roll temperature of 390 F. and hot roll surface speed of 500 meters per minute and at a twist tube speed of 8500 r.p.m.; the theoretical false twist is 54 turns per inch.

Example 9 The Example 7 process is carried out but at a twist tube speed of 10,000 r.p.m.; the theoretical false twist is 63 turns per inch.

Example 10 In a similar manner there is processed 70 denier, 17 filament, Z-turn per inch, semidull nylon-66 yarn (which, it may be noted, has a radius of 0.0035 inch) at a hot roll temperature of 399 F., a take-up roll speed of 600 meters per minute and a twist tube speed of 10,000 r.p.m.; the theoretical false twist is 76 turns per inch.

8 Example 11 Two threadlines of 15 denier monofilament nylon-66 yarn are processed simultaneously by an apparatus as shown in the drawing. The hot roll has a four-inch radius and a six-inch width. The two ends of monofilament nylon-66 yarn are combined upstream of the twist holdback guide and this combined strand is introduced into contact with the hot roll surface at a point one inch from theend of the cylinder to the observers right and allowed to roll to the. end of the cylinder on the observers left; the yarn is withdrawn from the hot roll surface about one .inch from the-left hand edge of the hot roll; a metal rod perpendicular'to the axial centerline of the hot roll is appropriately placed to define this limit; 17% inches of the two combined strands of nylon-66 monofilament yarn are wrapped about 242 degrees of the circumference of the hot roll. The surface temperature of the hot roll is 430 F. and the hot roll surface speed is 500.2 meters per minute. The twist tube has an internal diameter of inch and rotates at 1 6,500 r.p.m. and the yarn has an entry angle of 43 and an exit angle of 56. Take-up roll 18 has a surface speed of 500.2 meters per minute. The two ends of monofilament nylon yarn that make up the combined strand of textured yarn leaving the take-up roll 18 are separated and each of these ends of textured monofilament 15 denier nylon yarn is now wound, independently, on separate packages at about 3 grams tension. The theoretical false twist level is 150 turns per inch. The textured monofilament yarn thus produced is alternately coiled and spiraled at a frequency and amplitude dependent upon the processing conditions. Each of the initial 15 denier monofilament nylon-66 yarn ends has a radius of 0.00088 inch.

The filamentary strands processed according to the present invention preferably are comprised of the more readily heat settable polymeric materials such as cellulose t'riacetate, i.e., acetylated cellulose having an acetyl value, calculated as combined acetic acid by weight, of at least 59%; a theoretical maximum being 62.5%, linear polyesters, polyamides such as nylon-6, nylon-66, etc., and the like. However, the filamentary strands may be comprised of secondary cellulose acetate having an acetyl value of about to 58%, but preferably the well-known secondary cellulose acetate of commerce having an acetyl value of about 53 to 55%, other cellulose esters such as cellulose propionate, cellulose butyrate, cellulose acetatepropionate or cellulose acetate-butyrate and cellulose ethers such as ethyl or benzyl cellulose, and blends of such organic derivatives of cellulose with fibers of other materials such as regenerated cellulose, e.g., viscose rayon or cuprammonium rayon, silk and viscous rayon or cuprammonium rayon themselves, polyurethanes, acrylonitrile polymers and copolymers, olefin polymers and copolymers, vinyl chloride and vinyl acetate polymers and copolymers, vinylidene cyanide polymers and copolymers, other thermoplastics, and the like; also, the filamentary strands may be mono, bi-, or multicomponent in composition. In any event, the filamentary composition is a matter of choice and essentially any may be used.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a method of bulking a filamentary strand comprising providing a toroidal surface having a filamentary strand contacting portion, at least part of said filamentry strand contacting portion having a high coefficient of friction with respect to a filamentary strand; longitudinally feeding said filamentary strand into contact with said toroidal surface at an entry angle of from about 30 to longitudinally moving such strand along and in contact with said toroidal surface in the axial direction; and withdrawing said strand from final contact with said toroidal surface at an exit angle of from about 30 to 90; the improvement comprising, longitudinally moving a filamentary strand toward said toroidal surface in a helical path of contact with a rotating heated surface thereby providing improved heat-setting of the filamentary strand.

2. The method of claim 1, wherein said heated surface has a linear speed of at least as great at the linear speed of the filamentary strand thereby causing the strand to roll on said heated surface, said rolling being caused by transverse frictional forces applied to said strand by said surface.

3. The method of claim 2, wherein said heated surface is at a temperature of from about 260 to 600 F. and is moved in the direction of the filamentary strand at a surface speed of from about 200 to 1500 meters per minute.

4. The method of claim 3, wherein said rotating heated surface has a radius of from about 1.5 to 5.0 inches, and the said strand forms a helical path on said heated surface resulting from withdrawing the strand from contact with the heated surface at a point axially removed from the point at which the strand is introduced into contact with the heated rotating surface of from 1.5 to 5.5 inches.

5. The method of claim 4, wherein said strand contacts from about 240 to 270 degrees of said rotating heated surface.

6. The method of claim 5, wherein the filamentary strand is a cellulosic ester.

7. The method of claim 6, wherein the speed of the filamentary strand across the toroidal surface is from about to 25% greater than the speed at which it subsequently is packaged.

8. Method according to claim 1, wherein a plurality of filamentary strands are passed together in contact with the rotating heated surface and through the rotating toroidal surface whereby said strands are false plied and false 10 twisted together and at least partially heat-set, and thereafter taking up said strands on separate takeup packages whereby the false plied and false twisted strands come unplied downstream of the toroidal surface.

9. In an apparatus for bulking a filamentary strand comprising a twist hold-back means, a rotatable ring having inner surfaces for operating upon the filamentary strand, at least part of the inner surfaces being comprised of a material having a high coefiicient of friction with respect to the filamentary strand, and means for moving the filamentary strand longitudinally in contact first with said twist hold-back means, then from said twist holdback to said inner surfaces of said ring; the improvement comprising, in combination therewith of a rotating heating surface thus providing the strand with a helical path of contact, said rotating heating surface being heated internally by a suitable heating means.

10. The false twist textured filamentary strand produced by the process of claim 1.

References Cited UNITED STATES PATENTS 3,009,312 11/1961 Seen et al 57-34 2,477,909 8/1949 Stockly 57-34 2,936,570 5/1960 Arthur et al. 57-157 2,963,848 12/ 1960 Finlayson et al. 57-34 2,977,745 4/1961 Neu et al. 57-34 3,094,834 6/1963 Deeley et al. 57-157 X 3,112,600 12/1963 Stoddard et all. 57-34 3,154,835 11/1964 Palma et al.

WILLIAM S. BURDEN, Primary Examiner.

US. Cl. X.R. 57-140, 157 

